This invention relates to respirator mass transfer devices such as heat exchanges and in particular to a new and useful hollow fiber mass transfer module and to a module construction.
This invention concerns a process for producing a hollow fiber mass transfer module in which a number of parallel hollow fibers are introduced into a housing and are tightly sealed to one another and to the inner wall of the housing with grout, with a first flow space being formed between the inner wall of the housing and the outsides of the hollow fibers, which is separated from the second flow space determined by the internal volumes of the hollow fibers. A module produced by this process is also described.
Hollow fiber mass transfer modules are produced in numerous different forms. Elongated, essentially cylindrical housing shapes are known, in which the hollow fibers extend coaxially with the housing from one end to the other. Designs of modules are also known in which the hollor fibers run in loops in the housing, so that the inlet and outlet openings are essentially in one plane.
Such hollow fiber mass transfer modules are used for selective mass transfer between two fluids (gas, liquid). One fluid flows in a first flow space on the outside of the hollow fibers, while the other fluid is contained in the second flow spaced determined by the internal volume of the hollow fibers. Since the walls of the hollow fibers preferably consist of semipermeable membranes, a selective passage of substances from one fluid into the other is possible.
Hollow fiber mass transfer modules, called "hollow fiber modules" below, are used in the medical sector in dialyzers, and in hemofiltration, and for other purposes.
Another application is in air humidifiers, which are used, for example, in combination with equipment for artificial respiration. Such respiratory humidifiers are described in German Pat. No. 26 17 985 and in European Pat. No. B1 0 009 543. In such hollow fiber modules used as respiratory humidifiers, relatively large amounts of a substance (water) and thermal energy are interchanged. In the same way, the module should have relatively low flow resistance in both flow spaces.
While the second flow space determined by the internal volumes of the hollow fibers can easily be enlarged by using hollow fibers with a relatively large diameter, or by a larger number of hollow fibers connected in parallel, difficulties arise in keeping the flow resistance relatively low between the outside of the hollow fibers, i.e., in the first flow space. If the elastic hollow fibers do not assume perfectly mutual separation and partly rest against one another, the flow resistance is substantially increased. Increasing the separation of the hollow fibers, which would preclude mutual contact, leads to an undesirable increase of the dimensions of the device.
Various ways of improving the flow characteristics on the outsides of the hollow fibers are known. Thus, for example, guide ribs have been incorporated into the housing that force a flow in the transverse direction. European Pat. No. A 0 005 866 provides for a hollow fiber module usable in combination with an artificial lung in which the hollow fibers are contracted in the central area of the module in order to avoid so-called "channeling", i.e., the occurrence of intensified flow between the bundle of hollow fibers and the housing wall. However, the aforementioned measures are inadequate, especially in cases in which high requirements are placed on the mass transfer with small dimensions of the hollow fiber module.